This invention relates to a suspension system for a bicycle or the like to improve the riding comfort thereof. More particularly, the invention relates to a shock absorbing system for use at the seat or other location on a bicycle to form a suspension system to dampen shocks incurred during riding thereof.
The comfort of the ride on bicycles or other similar vehicles has escalated in importance as the popularity and use of such vehicles has expanded. For example, bicycles are now manufactured which are known as mountain bikes or ATB's (All Terrain Bicycle) which are constructed to be used in off-road environments. In these particular situations, the comfort of the ride is particularly important. The comfort is also important with road use of bicycles as the length of the ride is usually significantly longer.
A variety of suspension systems have been developed for bicycles or the like. These include shock absorbing means coupled with the frame of the bicycle and to the wheels thereof so as to absorb shocks imposed on the wheels during riding. A few examples of such systems are shown in U.S. Pat. Nos. 4,576,393 and 4,421,337. These systems provide relative movement between the wheels and the frame of the bicycle, and necessarily include toggle links or other hinge means to allow pivotal motion at the location where the wheels are secured to the frame of the bicycle.
A similar system is shown in U.S. Pat. No. 4,582,343, wherein a rear-wheel suspension system includes a shock absorber, having its outer housing incorporated as a structural element of the frame of the bicycle and connected to a linkage system to allow relative movement of the rear wheel. This system also incorporates a rider-controlled valve for hydraulically locking and unlocking the shock absorber to engage the suspension system when desired by the rider.
There are also known bicycle suspension systems having a shock absorbing means forming part of the frame of the bicycle. One system, in U.S. Pat. No. 4,679,811, shows a shock absorber mounted in a tube of the frame of the bicycle which has its piston connected to a separate rear frame or swing-arm wheel mount for the rear wheel. This system also comprises an actuating cable coupled with the shock absorber of the system to lock the shock absorber and prevent the suspension action thereof when desired.
Similarly, the front wheels of the bicycle have also been provided with a suspension system such as shown in U.S. Pat. No. 3,208,767, wherein coacting splined tubular members are slidably engaged to allow vertical movement of the wheel to which the suspension is connected but to prevent relative rotation of the tubular members.
Some proposed systems to isolate shocks imposed on bicycles and similar vehicles have included the mounting of coil springs onto the bottom of the seat on which the rider rests or to the seat frame to cushion shock to some degree. Other systems provide relative movement between the seat of the bicycle on which the rider will be supported and the frame of the bicycle, to thereby absorb shocks imposed on the bicycle and to provide a smoother ride. One proposal uses spring posts with external springs and key slots designed to dampen the jarring of a bicycle frame and seat as shown in U.S. Pat. No. 4,736,983. The coil spring in this invention is received on a post to which the seat of the bicycle may be mounted and the whole assembly is prevented against rotation to maintain the seat in alignment during riding of the bicycle.
In this type of system, a shock absorbing mechanism is exposed to the atmosphere and is, therefore, subject to corrosion which will limit the life expectancy and functioning of the apparatus. Similarly, the key slot provided to prevent rotation of the post to which the seat is attached is also exposed to the environment and may gather dirt or other debris, thereby inhibiting relative movement of the outer sleeve. It is also seen that the device has no means by which the rider can vary the amount of dampening provided by the system and will not be effective over a wide range of riders which may utilize the system and over a broad range of road or off-road conditions.
In another system, as shown in U.S. Pat. No. 4,182,508, a post to which the seat is mounted which is slidable telescopically within another fixed post, acted on by a spring to act as a shock absorber. This system includes an optional locking of the two posts together to eliminate the cushioning effect afforded thereby and fully encloses the spring mechanism to prevent corrosion and malfunctioning. This system also includes a slot provided on an inner tubular member in which an inwardly protruding key formation on an outer tubular member is disposed to prevent relative rotation between the tubular members. This system again shows a non-rotation, free spring seat post with no hydraulic dampening or lubrication of the sliding mechanisms to extend the useful life and function of the system.
Another known shock absorber is shown in U.S. Pat. No. 3,891,236, again showing a shock absorber to act as a support for the seat of the bicycle. In this system, a shock absorber includes an oil cylinder which is filled slidably but nonrotatably in an outer tubular member. The oil cylinder rests on a spring and a piston extends therein to provide a dampening action in the system. The absorber utilizes polygonal shaped tubular members to prevent relative rotation therebetween, with a separate dampening chamber as described. The polygonal slide tubes are separate from the oil chamber and receive no lubrication during use. A spring rate is variable by changing the distance of the dampening chamber to the lower spring chamber which reduces the distance of travel of the seat directly. Therefore, the heavier rider must increase the spring rate as needed and, in doing so, will lose seat movement which may be important under some conditions.
It is seen that prior art systems provide different suspension system designs, some of which include relatively complex toggle systems to yield relative movement between the wheels of the bicycle and the frame. These systems must be incorporated into the manufacture of the bicycle and cannot be utilized with existing bicycles not having a suspension system.
Other suspension systems have included shock absorbing means which may be incorporated into an existing bicycle. These designs have included telescopically slidable members which are prevented against rotation relative to one another and which are non-lubricated and may be exposed to atmospheric conditions. Some systems have not been adjustable while others include adjustment of the preload on a spring mechanism to accommodate heavier loads. Unfortunately, the adjustment of the preload on the spring also reduces the travel distance of the seat or other portion of the bicycle and thereby inhibits use of the system under some circumstances.